COHERENCY EFFECTS DURING PRECIPITATE COARSENING IN PARTIALLY-STABILIZED ZIRCONIAS

Precipitate morphology and distribution have been studied in two Mg based partially stabilized zirconias as a function of aging time at 1420-degrees-C. In both alloys, the number of precipitate variants locally present decreased from three to one, and the variant dropout could be described by Avrami kinetics. The aspect ratio of the precipitates increased as a function of aging time from an initial value of almost-equal-to 5, and the habit changed from {100} to one of the form {hhl}. Many of the observed microstructural features were predicted either qualitatively or quantitatively by the linear elastic theory developed primarily by Khachaturyan. This theory assumes precipitate morphology and distribution to be controlled by coherency stresses across the precipitate/matrix interface.